Vegetables are the most important source of compounds with chemopreventive activity: among them, the isothiocyanates (ITCs) produced in Brassicaceae (e.g. broccoli, Brussels sprouts, cauliflower, etc.) have currently drawn a lot of interest since Sidransky's first study about ITC-induced tumor growth inhibition [1].
In vegetables, ITCs are stored in the form of inactive precursors called glucosinolates (GLs) and can be released after tissue damage by enzymatic hydrolysis involving myrosinase (MYR, E.C. 1.2.1.147), a thioglucoside glucohydrolase that is physically separated from GLs under normal conditions [2,3].
As the intestinal microflora of mammals, including humans, has myrosinase-like activity, GLs can also be converted into ITCs in their digestive tract [4,5].
ITCs have been reported to be inhibitors of tumor growth in different in vivo preclinical studies [6-8] and moreover epidemiological studies have shown an inverse relationship between dietary consumption of Brassicaceae and risk of developing lung, breast and colon cancer [9-11].
ITCs have many effects through which they exhibit their protective action against cancer progression: they can i) induce phase-2-enzymes like glutathione-S-transferase (GST) and quinone-reductase (QR) [12-15] through a Nrf-2 pathway, ii) cause cell cycle arrest and apoptosis [16-18], iii) inhibit phase-I-enzymes and NF-kB related genes [19,20].
Sulforaphane has been extensively studied in recent years, due to its role as a chemopreventive agent and various studies have demonstrated its potential use as a novel chemotherapeutic compound [7, 11, 20].
Glucomoringin (GMG) is an uncommon member of the glucosinolates (GLs) family and presents a unique characteristic consisting in a second saccharidic residue in its side chain. This GLs is a typical secondary metabolite present in vegetables belonging to the genus Moringaceae that consists of 14 species, among which M. oleifera is the most widely distributed. M. oleifera is a multipurpose tree which grows in many tropical or equatorial regions. The medical value of the seeds and other part of the plant have long been recognized in folk medicine [21]. The glycosylated isothiocyanates (GMG-ITC), resulting from myrosinase-hydrolysis of GMG, has been shown to exhibit a broad biological activity and it was also shown to exert an effective antitumor promoting activity [22]. GMG-ITC can be purified in high amount starting from pure GMG. GMG-ITC is a solid, odourless and stable compound at room temperature differing from others natural bioactive ITCs which are liquid, volatile, with pungent odour.
Multiple myeloma is a malignant disease of plasma cells that is characterized by skeletal destruction, renal failure, anemia and hypercalcemia [23]. The median age at diagnosis is 68 years. Myeloma accounts for 1% of all malignant disease in white population and 2% in black population and 13% and 33% respectively, of all hematological cancers [24].
Treatments for myeloma include supportive treatment and infusional chemotherapy followed for younger patients by high dose chemotherapy and an autologous transplant [25]. Exploitation of the understanding of the biology of myelomas lead to development of new therapeutic approaches[26]. Although major progress has been made in treating myeloma with this new therapies, there is no role at present for the replacement of the standard cure. Thus, there is a continuing need for new, more active and/or alternative agents.